MSVC: Don't link libpgcommon into pgcrypto.

Doing so was useful in 273c458a but
became obsolete when 818fd4a6 caused
postgres.exe to provide the relevant symbols.  No other loadable module
links to libpgcommon directly.

src/tools/msvc/Mkvcbuild.pm

@@ -451,7 +451,6 @@ sub mkvcbuild
 			'imath.c');
 	}
 	$pgcrypto->AddReference($postgres);
-	$pgcrypto->AddReference($libpgcommon);
 	$pgcrypto->AddLibrary('ws2_32.lib');
 	my $mf = Project::read_file('contrib/pgcrypto/Makefile');
 	GenerateContribSqlFiles('pgcrypto', $mf);